1. Field of the Invention
The present invention relates to an electrode for an all solid polymer battery mainly containing a polymer and a lithium salt as an electrolyte phase, and relates to a method for manufacturing the electrode and to a battery using the same.
2. Description of the Related Art
In recent years, as large capacity power sources of electric vehicles, hybrid electric vehicles, and the like, lithium ion secondary batteries which can attain high energy and power densities have been developed. The lithium ion secondary batteries have a basic construction as follows. A positive electrode layer includes an aluminum collector to which a positive electrode active material such as lithium cobaltate (LiCoO2) and a conductive material such as acetylene black are applied using a binder. A negative electrode layer includes a copper collector to which a negative electrode active material such as carbon particles is applied using a binder. The positive and negative electrode layers are arranged with a porous polyolefin film separator interposed therebetween and are filled with a non-aqueous electrolytic solution containing LiPF6 and the like.
When applying the lithium ion secondary batteries to the electric vehicles and the like, single cells having this construction are connected in series to construct a battery module unit. Further, an assembled battery is constructed by connecting these battery module units in series.
In view of the energy density and the power density of batteries, there have been demands for improvement in connection resistances between cells and between modules, in space and in weight. Recently, a battery employing a bipolar electrode unit has been proposed. In this bipolar electrode unit, the connection resistance between cells can be reduced and downsizing thereof can be expected (see Japanese Patent Application Laid-Open No. H 11-204136). In this proposal, a so-called clad material made by rolling two types of metal foils is used for the collector, and a gel electrolyte is used for the electrolyte. Therefore, a liquid junction could occur between cells, so it is essential to hermetically seal each cell. If a solid polymer electrolyte is used instead of this gel electrolyte, the hermetic seal is not required, and thus a practical bipolar battery can be constructed (see Japanese Patent Application Laid-Open Nos. 2000-100471 and 2002-75455). In the bipolar battery, which is an all solid polymer battery including the solid polymer electrolyte as the electrolyte, there is an advantage of having extremely high reliability without liquid leakage, gas generation, and the like since a liquid electrolyte is not contained. In the negative electrode layer of such an all solid polymer battery, carbon particles are usually employed as the negative electrode active material due to being excellent in terms of battery characteristics and cost efficiency.